I am a heavy online video service user and a while ago I noticed that I had more and more trouble getting smooth video playback on Youtube, Vimeo and other streaming media services.

Don't get me wrong, the video is decoded nicely, my computer doesn't suffer from dropped frames, artifacts or any of the such.

It just lacks smoothness, i.e. not every frame has the same duration. Thus, movement seems jerky; video "stutters".

First, I want to point out that I noticed the issue on several machines running different hardware. My main PC is a desktop computer with AMD X4 955 CPU, 8 GiB DDR3, AMD HD5850 GPU and Windows 7 64 bits OS. I also tested on my laptop which is running a Core i7 3520m CPU, 6 GiB DDR3 and integrated HD4000 graphics. All runs on latest stable drivers of course.

Same jerkiness issue is present on both machines.

Then I tried using different web browsers. Firefox (26.0), Chrome (32) or IE (11.0.96) all demonstrated the same issue when playing back the same youtube video on all three browsers. Only left common denominator was Flash Player.

So I tested opening the videos (WebM/H264 MP4 bitstream) outside of the browser, using a more conventional media player. Opening the files in VLC showed very good results with extremely smooth playback (as initially expected from a 30 fps video). The results were expectedly as good in MPC-HC using EVR for rendering and more surprisingly also as good when opening the file in Firefox and letting the browser itself decode it with its own implementations of the decoders.

So basically, playing back the youtube video is an issue ONLY when doing it through Flash Player. Same phenomenon happens on other Flash-based video streaming sites such as Vimeo.

To be perfectly sure it wasn't my mind tricking me into the perceived jerkiness, I installed the FRAPS software in order to do some benchmarks on the rendering. I then plotted the amount of time each frame of the video is displayed, as measured by FRAPS

The test video was running at 25 frames per second which means that "optimum" playback displays each frame during exactly 40 milliseconds. To keep sync with the 60hz screen, it is not possible to display 40ms frames, so I would expect to see optimal as a perfect 2:2:3:2:3 pulldown meaning for "smooth video":

- frame 0 mod 5 of the video is displayed during 2/60 sec (33.333 ms)

- frame 1 mod 5 : 2/60 sec (33.333 ms)

- frame 2 mod 5 : 3/60 sec (50 ms)

- frame 3 mod 5 : 2/60 sec (33.333 ms)

- frame 4 mod 5 : 3/60 sec (50 ms)

and repeat.

This is what most v-synched video players (MPC-HC for instance) clearly do, and it gives a smooth playback.

Here is the result from the benchmark (Using Flash Player 12.0.0.43 and Chrome 32).

Y axis is the time each frame is displayed in milliseconds and X axis is the # of the frame

As you can see there is something clearly wrong in this pattern. It doesn't follow proper pulldown pattern; some frames are displayed for as less as 1 ms and some other are displayed for 60 ms which should never happen in optimal conditions. This, along with eye observation, further proves that video playback is not smooth.

Here is the result for the same video played in VLC media player without any vertical synchronization (bare decoding and rendering) :

As expected, silk-smooth 40 ms displaying time for each frame. Resulting video displayed is perfectly smooth.

Out of curiosity, I tried downgrading to former versions of Flash Player, because I remembered that I didn't seem to have this issue in the past.

Here's the result with Flash 11.7

Wow! What a surprise. The video feels smoother with an older version of Flash?! It's still far from perfect playback but the sole fact that going to a less advanced version means better playback is mesmerizing.

What happens if I go even further back in time? Let's try with flash 11.4 from August 2012 (gosh that's old)

Whaaat??? Almost judder-free pulldown? With this anciant version of Flash? What is going on?

Compare that chart with the first one, the difference going back one and a half years makes is absolutely astonishing.

I think I went deep enough into the demonstration, and despite all the warnings of "outdated version", Flash 11.4 does a better job at playing back youtube videos than 11.7... and a LOT BETTER than 12.0! What is going on?

Something definitely needs to be issued there. It seems very well that Flash Player has actually gotten worse and worse since 11.4.

Thanks for reading.

PS : I tried with both hardware acceleration on and off on all decoders including Flash Player, with similar end results (other than CPU % occupancy)

PS2 : I intentionnaly ignored Youtube HTML5 player for decoding as it is not a final product and it has nothing to do with the discussion on Flash Player.

It bugs me too but I think most people don't notice or care. Some Flash players like Comcast's are especially bad. But Silverlight (e.g. Netflix) and even the YouTube HTML5 player stutter to some degree. If I right-click on a YouTube HTML5 video and choose "stats for nerds", I see something like 599 frames decoded/parsed/presented but only 571 frames painted, meaning it's skipping about 5% of the frames for some reason. If I download the same YouTube video as an MP4 file and play it in Windows Media Player, the stuttering is gone. Is it more of a general problem with video inside web browsers?

I have a high-end PC and both Media Player and Media Center play perfectly smooth. What's funny is that many people tell you to turn OFF hardware acceleration as a solution, which is counterintuitive and doesn't work anyway, as you noted.

I have been having the exact same problem (as have many others), and it's been going on for years.

Just like you, I experience bad video judder with all fairly recent versions of Flash, but this never used to be a problem in the past.

It recently got to the point where I became so annoyed with it ruining my viewing experience that I decided to try older versions just to see if playback really did used to be as smooth as I remembered.

I therefore worked my way back through the versions. My testing was no where near as scientific as your tests; I was just using the same familiar video clip of mine that I also had a local copy of (for comparison).

In my tests (based purely on viewing) I found that all versions juddered and did not get smooth until I got back as far as version 10.3.183.50. That version worked really well for me.

I would happily use an old version in order to make video watchable and enjoyable again, if it weren't for the fact that Flash is used for many things other than video and can therefore be compromised by malicious sites. Couple this with the fact that it's written by Adobe, and that's reason enough to be scared. Hell, it's bad enough using the latest version, never mind an old one.

Given that Flash is so often used for watching video, I can't believe that Adobe have allowed such appalling playback to persist for years without addressing the issue.